Affecting <input pattern> now sets u flag for regular expressions

Published: | Categories: HTML

Description

The pattern attribute on the <input> element, introduced with HTML5, is used to check the entered value against the author-defined regular expression. Starting with Firefox 46, the new u flag, introduced with ECMAScript 2015 (ES6), is set for the expression according to the latest HTML spec, treating it as a sequence of Unicode code points. Therefore, an unnecessary or invalid escape in the pattern such as [\@\%] will raise a SyntaxError saying “invalid identity escape in regular expression” and the validation will fail.

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